Different useful approaches of implementing real-time AI?
About 15 years ago, John Laird's group at Michigan used the Soar rule-based architecture to play several FPS games effectively (Quake II, Descent III):

http://ai.eecs.umich.edu/people/laird/games_research.html

Here's Laird's overview article from 'Computer':

https://www.researchgate.net/profile/John_Laird/publication/2955463_Laird_JE_Using_a_computer_game_to_develop_advanced_AI_Computer_34_70-75/links/54d0f59a0cf20323c21a1bd7/Laird-JE-Using-a-computer-game-to-develop-advanced-AI-Computer-34-70-75.pdf